Electrical switch



Nov. 9, 1954 E. P. BULLARD m ELECTRICAL SWITCH Original Filed Nov. 18, 1947 DWI-\RU F. BuL L ARD HI United States Patent 0 ELECTRICAL SWITCH Edward P. Bullard HI, Wethersfield, Conn., assignor to The Ballard Company, a corporation of Connecticut Original application November 18, 1947, Serial No. 786,772, now Patent No. 2,623,970, dated December 30, 1952. Divided and this application November 21, 1951, Serial No. 257,557

7 Claims. (Cl. 20(l18) This invention relates to electric circuit-making switches, and particularly to a new and improved switch that is capable of repetitive use with extremely accurate results. This is a division of application Serial Number 786,772, filed November 18, 1947, Patent Number 2,623,970, which is a division of application Serial Number 586,799, filed April 5, 1945, Patent Number 2,511,821, which latter is a division of application Serial Number 541,986, filed June 24, 1944, Patent Number 2,528,736, all in the name of Edward P. Bullard III.

Ordinarily, the accuracy that can be obtained in the operation of machine tools, and particularly in the automatic-cycle operation of machine tools is limited by the accuracy that can be obtained with certain essential elements of the automatic control. For example, when electrical circuits are employed to control the movement of a member, the accuracy that can be obtained is limited by the accuracy of the operating parts of the electrical circuit, and particularly by the accuracy of those parts which are utilized repeatedly to effect stopping of the movement of the member such as trip switches.

Machine tool operation requires an accuracy, in stopping the movement of a tool, in the nature of .0005 of an inch. Not only must such accuracy be produced, but it must consistently be maintained regardless of the rate at which the tool is moved. Prior known electrical devices including contact-making switches for controlling the movement of a tool fail to produce accuracies of the order required in the machine tool control as set forth above.

Certain prior-known switches employ metal-flexing members that can be operated in response to tool movement. The accuracy of such switches is limited because the metal-flexing member fails to respond at exactly the same point of tool movement upon repeated operations under the same conditions. Plunger-type switches of the prior art are not reliable because their accuracy is directly affected by the action of the movable member that operates them. All prior-known switches are of relatively large size so that employment of any substantial number such as thirty or forty of such switches in a unit becomes impractically large and cumbersome. An additional disadvantage of prior-known plunger-type switches is that the impact between the plunger and its movable actuator materially afiects the accuracy of the switch often causing the contacts to close prematurely.

Objects of the present invention include the provision of an elecrical circuit-making switch that will overcome the above as well as other disadvantages of prior-known switches; the provision of a plunger-type electrical switch in which the plunger is moved to contact-making position by a device designed to provide a minimum of side thrust to the plunger; the provision of such a switch in which the contact-making action thereof is independent of the impact incident to switch actuation by a movable member; the provision of such a switch in which the plunger velocity increases from a minimum as it moves toward contact-making position; the provision of such a switch in which as many as forty can be arranged side by side in a space in the neighborhood of ten inches; and the provision of such a switch which can be operated with equal facility by a movable member approaching it from either of two directions.

The above, as well as other objects and novel features of the invention, will become apparent from the following specification and accompanying drawing, in which:

Figure 1 is an elevational view of an electrical circuitmaking switch to which the principles of the present 1nvention have been applied;

Fig. 2 is a view of the apparatus shown in Fig. l, as viewed when looking in the direction of the arrows 2-2 of Pi 1;

Fig. 3 is a view of the apparatus shown in Fig. 1, as viewed when looking in the direction of the arrows 3-3 of Fig. 1; and

Fig. 4 is a perspective view of a detail of the switch.

The embodiment disclosed in the present case deals with the employment of a relatively large number of switches arranged in closely spaced relation, and to separate actuators for each switch, which latter are adjustable throughout the entire path of travel of a movable member controlled by the operation of the switches.

Referring to Fig. 1, supports 10 and 11 are spaced apart an amount proportional, and preferably equal to the total distance of movement of a movable machine tool member to which an arm 12 of insulating material is rigidly attached. A metallic body 13 is fixed to the arm 12 and is provided with a series of cylindrical passages 14 arranged in closely spaced aligned relation for the reception of individual plunger contacts 15 of separate switches. The present embodiment of the invention utilizes in the neighborhood of forty switches which are unitarily movable, with the member to be controlled, between the supports 10 and 11. It is evident, therefore, that a main consideration of the design of the switches is that as many as forty or more may be mounted for movement with the movable member and still consume little space. Actually, in the practical embodiment, passages 14 are located on inch centers. Since all of the switches are identical, only one will specifically be described.

Each plunger 15 is provided with a portion 16 of reduced diameter that extends upwardly through a hole 17, within the arm 12, that is aligned with a passage 14. Spring 18 surrounds the reduced diameter portion 16 of plunger 15 and is compressed between the arm 12 and the shoulder between the large and small diameter portions of plunger 15. Spring contact members 19 for adjacent plungers 15 are arranged on alternative sides of the arm 12, and each is provided with a contact 26 that overlies the top of an opening 17. Accordingly, spring 18 urges plunger 15 out of contact-making position; and axial movement of plunger 15 in opposition to the action of spring 18 effects contact between the end of plunger 15 and contact 20. In order to insure uniform action of plunger 15 under the same operating conditions, it has been found important to eliminate as much as possible side thrust between the plunger 15 and the hole 14 within which it reciprocates. Excessive side thrust at this location causes unpredictable action of plunger 15 especially when wear between the plunger and hole occurs incident to such side thrust.

As previously stated, the diameter of plunger 15 must be relatively small so that a plurality of switches consume relatively little space. Should plunger 15 be moved axially by the usual impact between it and a member moving at right angles to the axis of the plunger 15, excessive unit side thrust would occur between plunger 15 and hole 1.4 causing excessive wear with attending error in switch actuation.

An additional consideration in the design of the switch to enable it accurately to make contact repeatedly under identical conditions is that the plunger 15 must not be subject to a sudden start of motion as is common in priorknown plunger switches Where impact between the plunger and a movable member is relied upon. Such sudden starting of the plunger, particularly when excessive side thrust is present, often causes the plunger to jump ahead and prematurely close the switch contacts.

In the present invention all of the above considerations have been taken into account in designing an actuator for moving the plunger 15 axially when the actuator is subject to a force at right angles to the axis of plunger 15. In other words, the electrical switch is so designed that the plunger 15 is moved into circuit-making position by an actuator along a path at right angles to the relative movement between the switch and a trip dog, and in which the trip dog, duringplunger movement and .prior to circuit-making condition, is not subjected to any force at right angles to said relative movement between the switch-and dog. .Referring to Figs. 1 and 3; the .lower portion of body '13 is provided with slots 21-aligned with the passages 14 for receiving plunger actuators 22 (Fig. 4). The actuators .22 include 'thin plate-like members having an arcuateedge .portion 23 and tangential surfaces 24 extending therefrom. The actuators.,22".are adapted to be assembled and dis-assembled fromthe body 13 without the use of separate fastening means, by trunnions 25, 25 that extend outwardly from eachfaceu The form of the lower portion of base 13 includes recesses 26, 26' on each side thereof adapted to .receive trunnions 25, 255; and shoulders. 27, 277 are provided for supporting the trunnions in fixedposition against the action of spring 18.

The one side of member'13 at the location of the recess 26' is further relieved byan undercut 28 for receiving the trunnions 25, during assembly and disassembly of the actuator 22. The position of the trunnions 25, 25 during assembly and dis-assembly is shown in dotted lines in Fig. 1. With trunnions 25 within the undercut 28, it is evident that the trunnions 25 can be pivoted about trunnions 25' in a manner to permit trunnions 25 to clear the shoulder 27. Upon movement of the actuator 22 in a manner to locate trunnions 25 on shoulder 27, trunnions 25 are forced out of the undercut 28, whereupon spring 18 seats trunnions 25' on shoulder 27. Disassembly of the actuator 22 is effected by a reverse of the action above described.

An abutment element 29 is integralwith, and extends downwardly from the actuator 22. It is adapted to receive they impact from a dog 30 that is adjustable throughout the length .of travel of a movable member to which the arm 12 is attached. The dog 30 is rectangular in construction, and can be approximately as thick as the distance between centers of the plungers 15. It is only essential that the dogs clear adjacent dogs permitting them to pass each other during adjustment. Each dog 30 is provided with parallel off-set passages 31, 32 adapted to receive wires 33 and 34, respectively. The wire 34 is rigidly mounted between supports 10, 11, while the wire 33 is adjustably mounted between said supports. The wire 33 extends beyond both supports and 11 and a spring 35 surrounds the one extension between the support 10 and a nut 36." The opposite end of wire 33 is provided with a screw thread of 40 threads per inch and a micrometer nut 37 is threaded onto said threaded extension into engagement with support 11. Each dog 30 includes two threaded openings 38, 39 into which screws 40, 41 are threaded, and which latter engage wire 33locking dog 30 thereto. Referring to Fig. 3, it is evident that wires 33 and 34 are 'ofiset. The reason for this is that adjacent dogs 30 are provided with alternate locations for wires 33 and 34. Thus, the first dog 30 on the left of Fig. 3 has wire 33 at the bottom and wire 34 at the top; while the second dog 30 from the left of Fig. 3, has wire 33 at the top and wire 34 at the bottom. This permits locating the micrometer nuts for adjacent dogs 39 in overlying relations which thereby consume less space. This necessitates using alternately long and short set screws 40, 41 in adjacent dogs 30 so that in each instance the dog 30 is locked to the wire 33.

The surfaces 42 and 43 of dogs 30 are parallel and normal to the direction of motion of the member to which arm 12 is attached. Accordingly, an abutting engagement between the element 29 and either surface 42 or 43 always occurs totally within a surface that is at right angles to the direction of relative movement between the dog 30 and the member to which arm 12 is attached. Accordingly, from the time of contact between dog 39 and element 29, until contact between 20 and the end of plunger occurs, there is no vertical force acting on dog 30. This is important to ensure repetitive operation of contact and plungerlS at exactly the same point.

The construction and arrangement of the various parts are such that the dog may initially be set roughly by loosening screws 41 41 and sliding the dog to the approximate desired location, after which screws 40, 41 are tightened thereby locking dog 3!) to wire 33. Final accurate adjustment of dog 30 is obtained by rotating the micrometer nut 37 which is provided with indices about its periphery that cooperate with a fixed index line on the ..supp.ort .11.

Movement of the member to which arm 12 is attached so that abutting engagement. occurs between element 29 and surface 42 causes trunnions 25 to seat on shoulder 27, and actuator 22 to pivot-on trunnions 25. This pivotal action causes the arcuate surface 23 and tangential surfaces 24 to force plunger 15 upwardly until contact is established between plunger 15 and contact 20. From an inspection of Fig. 1, it is evident that, by virtue of the arcuate surface 23, the initial pivotal movement of actuator 22 causes initial upward movement of plunger 15 at a relatively slow rate, gradually increasing due to the increasing distance between the point of contact of plunger 15 and actuator 22, and the trunnions 25. For this reason, any severe impact between surface 42 and element 29 is transferred into a rolling action about trunnions 25 in a manner such that plunger 15 initially begins to. move upwardly at a ,slow. rate which is independent of the impact between the surface Y42 and element 29.

' Should the switch move in a direction such that element 29 abuts surface 43, the same, action occurs with actuator 22 pivoting abouttrunnions '25.

Since the actuatorr22 pivots when impact occurs between element 29 and surfaces 42 or 43, the side thrust of plunger 15 in passage 14 is independent of such impact or abutment force. Accordingly, the plunger-15 can be made as small in diameter as desired without building up va detrimentally-high unit side thrust pressure between it and passage 14 which occurs in prior-known plunger-type switches.

Although the various features of the improved switch have been shown and described in detail to fullydisclose one. embodiment of the invention, it will be evident that numerous changes can be made in such details, and certain features can be used without others,,without departing from the principles of the invention.

What is claimed is:

1. Apparatus comprising in combination, a frame; a plurality of supports mounted in said frame; a dog slidably mounted on each of said supports; means for releasably fixing said dogs to their supports; a plurality of electrical switches, one for. each dog, said switches being adapted to be moved relative to said frame; contact means for each switch; and a .pivotally-mounted actuator including means adapted to abut said dog within a surface that is at all times maintained at right angles to the direction of said relative. movement.

2. Apparatus comprising in combination, a frame; a plurality of supports mounted in said frame; a dog adapted adjustably to be mounted on each. of said supports; a plurality of electrical switches, one for each dog and located in cooperative position relatively to its dog; contact means associated with each switch; and a rigid structure including a pivotally-mounted member between each said contact means and its dog.

3. Apparatus comprising in combination, a frame; a plurality of supports mounted in said frame; a dog adapted adjustably to be mounted on each of said supports; a plurality of electrical switches, one for each dog and located in cooperative position relatively to its dog; a contact for each switch including a part resiliently .urged against a rigid support,- and a rigid part movable .relatively to said rigid support; and a pivotally-mounted rigid member maintained in contact with said rigid part at all times.

4. In a switch device, a body; a passage in-said body; a plunger within said passage; a contact adapted to be engaged by said plunger when the plunger is moved axially within said passage; an actuator for administering an axial thrust to said plunger; and a dog relatively movable at right angles to the longitudinal axis of said plunger, said actuator including a portion adapted to be engaged by said dog such that, prior to engagement between said plunger and contact, said dog is subjected to no forces at right angles to said relative motion.

5. In a switch, a body; a passage in said body; a plunger within said passage; a contact adapted to be engaged by said plunger when the plunger is moved axially within said passage; an actuator for administering an axial thrust to said plunger; and a dog relatively movable in either direction at right angles to the longitudinal axis of said plunger, said actuator including a portion adapted to be-engaged by said .dog such that,

prior to engagement between said plunger and contact, said dog is subjected to no forces at right angles to said relative motion.

6. In a switch, a body; a passage in said body; a plunger within said passage; a contact adapted to be engaged by said plunger when the plunger is moved axially within said passage; a pivotally-mounted actuator for administering an axial thrust to said plunger; and a dog relatively movable in either direction at right angles to the longitudinal axis of said plunger, said actuator including a portion adapted to be engaged by said dog such that, prior to engagement between said plunger and contact,

said dog is subjected to no forces at right angles to said relative motion.

7. Apparatus comprising in combination, a frame; a 15 rigid member maintained in contact with said rigid part at all times.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,952,153 Young Mar. 27, 1934 2,059,023 Perry Oct. 27, 1936 2,097,537 Snyder .Nov. 2, 1937 2,133,545 Krieger Oct. 18, 1938 2,368,083 Adam Ian. 30, 1945 

